The invention relates generally to techniques for interrogating optic sensors of the type that modulate electromagnetic energy in relation to a number of measured or sensed parameters such as rotational speed, proximity of a target, position encoding and so on. More particularly, the invention relates to system architectures that involve the use of a plurality of such sensors.
Many types of optic sensors have been developed and the extent of their commercial use is only recently beginning to be realized. A typical optic sensor uses a source of light that is transmitted to the sensor and a light detector for transducing the modulated light into an electrical signal for further processing. Transmission of the light is commonly done with optic fibers and associated optic couplings and connectors.
For example, recently an improved sensor design has been disclosed in U.S. Pat. No. 5,149,962, issued to Maurice, which patent is owned in common by the assignee of the instant application. This sensor is a magneto-optic type sensor that uses a bi-directional sensing technique so that the optic signals are self-referenced and provide an inherent built-in-test capability. The improved sensor also features the use of photoelectric devices, such as LEDs, that individually perform a dual function as light source and detector for interrogating the sensor bi-directionally. The use of dual-function devices significantly reduces the sensor envelope and simplifies the sensor design and reduces overall cost.
Because an optic sensor requires at least one light source and light detector for operation, systems that use a plurality of optic sensors can easily involve the use of a large number of photoelectric devices so that all the sensors can be interrogated. Although optic switches could be used to reduce the number of photo-sensors, such devices are expensive and would require complicated timing and control logic. The objective exists, therefore, for a system architecture or network that can use a plurality of optic sensors with a reduced number of light sources and detectors to reduce system complexity and cost.